Method and system for quantitative imaging

ABSTRACT

A system and method for digital x-ray imaging. The method includes emitting a first and second collimated x-ray beam from an x-ray source disposed in a first and second position, respectively. The first and second collimated x-ray beam is directed onto an identified region of interest (ROI) wherein a first and second ROI image is captured, respectively, when the x-ray source is disposed in the first and second position, respectively. The first and second ROI images are processed to extract features from each of the first and second ROI images. The extracted features are analyzed, and an indicator of a disease is generated responsive to the extracted features. The indicator can be stored, displayed, or transmitted. The first and second x-ray sources can be the same or different x-ray sources.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional application U.S.Ser. No. 61/712,480, provisionally filed on Oct. 11, 2012 entitled“METHOD AND SYSTEM FOR QUANTITATIVE IMAGING OF INTENSIVE CARE UNITPATIENTS”, in the names of Foos et al, which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The invention relates generally to the field of medical imaging.

BACKGROUND

The chest x-ray is a useful diagnostic tool that assists in detecting anumber of patient conditions and for imaging a range of skeletal andorgan structures. Radiographic images of the chest can be useful fordetection of lung nodules and other features that indicate lung cancerand other pathologic structures. In clinical applications such as in theIntensive Care Unit (ICU), the chest x-ray can have particular value forindicating pneumothorax and other clinical conditions.

SUMMARY

Certain embodiments described herein address the need for quantitativeanalysis of Intensive Care Unit (ICU) patient images.

Another aspect of the present invention is to distinguish among thepossible causes of regions of lung opacity.

Any aspects provided are given only by way of illustrative example, andsuch objects may be exemplary of one or more embodiments of theinvention. Other desirable objectives and advantages inherently achievedby the disclosed invention may occur or become apparent to those skilledin the art. The invention is defined by the appended claims.

According to one aspect of the invention, there is provided a digitalx-ray imaging system, comprising: an x-ray source adapted to emit anx-ray beam; a collimator to collimate the x-ray beam to an identifiedregion of interest; a positioning system to translate or rotate thex-ray source from a first position to a second position, wherein thesecond position is different than the first position; a digital x-raydetector adapted to capture a first image of the region of interest whenthe x-ray source is in the first position, and capture a second image ofthe region of interest when the x-ray source is in the second position;a processing engine to extract features from each of the region ofinterest of the first and second captured images; and an analyzeranalyzing the extracted features and generating an indicator of adisease responsive to the extracted features.

According to another aspect of the invention, there is provided adigital x-ray imaging system, comprising: an x-ray source adapted toemit an x-ray beam; a collimator to collimate the x-ray beam to anidentified region of interest; a first x-ray source in a first position;a second x-ray source in a second position, wherein the second positionis different than the first position; a digital x-ray detector adaptedto capture a first image of the region of interest using the first x-raysource disposed in the first position, and capture a second image of theregion of interest using the second x-ray source disposed in the secondposition; a processing engine to extract features from each of theregion of interest of the first and second captured images; and ananalyzer analyzing the extracted features and generating an indicator ofa disease responsive to the extracted features.

According to a further aspect of the invention, there is provided amethod for digital x-ray imaging, comprising: emitting a firstcollimated x-ray beam from an x-ray source disposed in a first position;directing the first collimated x-ray beam onto an identified region ofinterest (ROI) and capturing a first ROI image; emitting a secondcollimated x-ray beam from the x-ray source disposed in a secondposition, wherein the second position is different than the firstposition; directing the second collimated x-ray beam onto the identifiedregion of interest and capturing a second ROI image; processing thefirst and second ROI images to extract features from each of the firstand second ROI images; analyzing the extracted features; generating atleast one indicator of a disease responsive to the analyzed extractedfeatures; and storing, displaying, or transmitting the at least oneindicator.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of theinvention will be apparent from the following more particulardescription of the embodiments of the invention, as illustrated in theaccompanying drawings. The elements of the drawings are not necessarilyto scale relative to each other.

FIG. 1 shows an x-ray imaging system according to an embodiment of thepresent invention.

FIG. 2 shows an x-ray imaging system according to an embodiment of thepresent invention.

FIG. 3 shows a full field for localization of an x-ray imaging systemaccording to an embodiment of the present invention.

FIG. 4 shows a region of interest field of an x-ray imaging systemaccording to an embodiment of the present invention.

FIGS. 5A and 5B show a wired detector arrangement of an imaging systemof FIG. 1.

FIG. 6 shows a wireless detector arrangement of an imaging system ofFIG. 1.

FIG. 7 shows an x-ray imaging system of FIG. 1 having a positioningsystem for translating and/or rotating an x-ray source.

FIG. 8 shows an x-ray imaging system of FIG. 1 having a positioningsystem having a plurality of x-ray sources.

FIGS. 9 and 10 show an exemplary radiographic imaging systems includingan x-ray source assembly having first and second (e.g., multiple)radiographic x-ray sources.

FIG. 11 generally illustrated a method according to the presentinvention.

FIG. 12 shows a method for one embodiment according to the presentinvention.

FIGS. 13A and 13B illustrate examples of an output.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following is a detailed description of the embodiments of theinvention, reference being made to the drawings in which the samereference numerals identify the same elements of structure in each ofthe several figures.

This disclosure describes a method and system that is suitable forquantitative analysis of Intensive Care Unit (ICU) patient images. Inparticular, the method and system is suitable for distinguishing amongthe possible causes of regions of lung opacity.

Opacity refers to an area that preferentially attenuates the x-ray beamand therefore appears more opaque than the surrounding area. Opacitiesin chest x-ray refer to white smudges on the lung areas. Normal lungsappear dark on x-ray films because they are filled with air. Anymaterial denser than air would appear as an opacity. This couldrepresent a collection of thickened lung tissue secondary to underinflation (not breathing deep) or pneumonia, or several blood vesselsand ribs overlying one another. For example, “suspicious faint opacityin upper lobes” may suggest a diagnosis of pulmonary tuberculosis or alung mass, depending on the characteristics of the opacity.

Mobile/portable x-ray radiographic imaging systems that can be wheeledup to a patient's bedside, such as in an Intensive Care Unit (ICU)facility, can be employed for imaging patients to evaluate patienthealth and determine appropriate/best treatment.

However, abnormal findings on portable chest x-ray images of ICUpatients are frequently nonspecific. Nonspecific findings are typicallyvisualized as regions of opacity in the lung, but without any clearindication of whether the pathology is in the airways (e.g., lungcollapse), airspaces (consolidation) or within the pleura (effusions).Establishing the correct diagnosis is desirable so as to initiateappropriate patient management.

Differentiating among types of pleural effusions is another common taskassisted by imaging in the ICU and can be challenging and critical topatient care. Various types of fluids can cause plural effusions [e.g.,blood (hemothorax), pus (pyothorax or empyema), and water/serous fluid(hydrothorax)]. Furthermore, each cause requires a different course ofaction.

Therefore, improved ability to identify the cause is beneficial. Thatis, knowing the cause with greater probability would be expected toenhance patient care.

In situations where mobile/portable radiographic imaging is foundinsufficient, Computed Tomography (CT) might be prescribed as itprovides a full 3D image. However, acquiring a CT image can bedisruptive to the patient who is in critical care. For example,obtaining a CT in such situations requires transporting an unstablepatient out of the ICU which increases risk to the patient's alreadycritical condition. An alternative to CT could be a bedside x-rayimaging system that is capable of providing quantitative informationthat will improve the specificity of findings that are identified onstandard portable chest radiography. Such a system would be beneficialbecause it would reduce the need to transport unstable ICU patients forCT exams.

This disclosure describes a method and system that is suitable forquantitative analysis, particularly for ICU patient images. Inparticular, the method and system is suitable for distinguishing amongthe possible causes of regions of lung opacity.

The system employs an x-ray imaging system for capturing a plurality ofx-ray images, wherein each image includes an identified region ofinterest (ROI). The system includes: a digital x-ray detector adaptedfor image acquisition; an x-ray generator/source adapted for x-rayexposures; a collimator adapted to focus/cone-down to a region ofinterest; and a positioning system that allows images of the identifiedregion of interest (ROI) to be captured with different geometries, x-rayfocus spot sizes, or other acquisition system parametric variations thatcan produce images of the ROI having different characteristicproperties.

In at least one arrangement, the digital x-ray detector includes adigital x-ray detector adapted for rapid sequential image acquisition,and high frame rate readout for an identified region of interest, forexample, an identified central region of the detector.

In another embodiment, the system is a digital mobile/portable x-rayimaging system.

A processing engine is employed to extract features from each of the ROIof the images. The extracted features are then analyzed using ananalyzer, such as a statistical predictive model or trained neuralnetwork. An output is generated from the analyzer which provides anindicator/representation of the probability that the opacity isindicative of a specified underlying cause.

In one arrangement, the region of interest is in the 4 cm×4 cm size. Assuch, a feature of imaging based on the ROI is that accumulated patientdose (from the x-ray imaging source) will be limited to a relativelysmaller anatomical region. The neural network or statistical predictivemodel can be calibrated accordingly, such as to the CT setup.

FIGS. 1 and 2 illustrated an exemplary digital mobile/portable x-rayimaging system.

The schematic block diagram of FIG. 1 shows a mobile digital radiographysystem 100 that obtains images of a patient 14 in an ICU or otherfacility and communicates with a number of medical archiving andradiology databases over a network 26. Among the databases thatcommunicate over network 26 are a Hospital Information System (HIS) 20,a Radiologist Information System 22, and a PACS 24. In addition, one ormore optional image processing workstations 30 also receive and processimages from mobile digital radiography system 100. Mobile digitalradiography system 100 can include a wireless interface 36 to network26, typically connecting to a wireless hub or similar datacommunications interface device. Those skilled in the art will recognizethat the use of a wireless interface offers an advantage for systemusability, flexibility, and information access, as describedsubsequently.

FIG. 2 shows a schematic block diagram of mobile digital radiographysystem 100 in one embodiment. A cart 40 having an x-ray source 34 withthe x-ray generator and related components for passing x-ray radiationthrough a portion of the patient's body and on to a digital detector 38.X-ray source 34 includes a collimator or collimating means to collimatethe emitted beam of x-ray. A computer 42, shown within cart 40 in thisembodiment, provides the control logic for controlling a number offunctions, including controlling the x-ray generation from x-ray source34, obtaining the digital image data from detector 38, and controllingthe transfer of data with network 26 and with one or more displayinterface units 32 that provide an operator interface display. Anoptional secondary display 80, such as a high-resolution displaymonitor, is also being provided as part of cart 40.

A detachable display interface units 32 can be used as portable operatorconsoles of mobile digital radiography system 100 for communication ofpatient images, patient data and history, instructions, and other data.Display interface unit 32 provides access to mobile digital radiographysystem 100 in a number of ways. For example, a technologist can usedisplay interface unit 32 as an operator console for obtaining workflowsequence instructions, obtaining information relevant to obtaining asuitable image for each patient, for entering of instructions forcontrolling the imaging apparatus itself such as for initiatingexposure, and for initial quality control (QC) checks of image quality.An attending physician 16 uses display interface 32 to enterinstructions and work orders for the image or images needed for aparticular patient. The ICU staff use display interface 32 to check thestatus of imaging requests and to obtain notification that requestedimages have been obtained. Display interface 32 also serves forinterpretation of the patient condition for another physician 16 at thebedside, allowing a comparison with data from prior examinations andallowing interpretation of proper positioning of tubing or other lines,for example.

FIG. 3 illustrates an x-ray beam emitted from x-ray source 34 beingdirected toward patient 14 for capturing of an x-ray image usingdetector 38. As illustrated, the x-ray beam emitted from x-ray source 34has not been collimated by a collimator, and thus is show as a fullfield of localization.

Referring to FIG. 4, the beam of light from x-ray source 34 has beencollimated by a collimator, and therefore, the beam of light emittedfrom x-ray source 34 has been collimated to a region of interest for thecapture of an image (i.e., and ROI image) by detector 38.

Collimators are well known to those skilled in the art, for example, asdescribed in U.S. Pat. No. 6,118,842 (Arai), incorporated herein byreference. Collimation can be used during the x-ray exposure to reduceunnecessary radiation to the anatomy that is irrelevant to diagnosis andto confine the x-rays to a local region.

FIGS. 5A and 5B show additional views of the system wherein a wiredarrangement is employed. As illustrated, the x-ray beam of light hasbeen collimated.

FIG. 6 shows the system wherein a wireless arrangement is employed. Asillustrated, the x-ray beam of light has been collimated.

FIG. 7 illustrates a positioning system to translate (arrow A) and/orrotate (arrow B) collimated light from x-ray source 34 to achieve depthinformation for the region of interest. By translating and/or rotatingx-ray source 34, a plurality of x-ray images—each image focusing the ROIat a different depth of the patient—can be acquired. Accordingly, thereis acquired a plurality of x-ray images achieving depth information.

Similarly, referring to FIG. 8, a stationary positioning systemcomprised of a plurality of x-ray sources can be employed. In thisarrangement, each x-ray source is disposed at a different angle/positionrelative to the patient, yet each x-ray source can be collimated to anidentified region of interest on the patient. With this arrangement,each x-ray image captures an image of the region of interest with adifferent geometry.

FIGS. 9 and 10 are a diagram that shows exemplary radiographic imagingsystems including an x-ray source assembly that can include first andsecond (e.g., multiple) radiographic x-ray sources. As shown, an x-raysource assembly 1040 of a radiographic imaging system can include afirst radiographic x-ray source and collimator, and a second x-raysource comprising a distributed source (e.g., rectangle in FIG. 9 andlinear in FIG. 10) that can be individually adjusted (e.g., collimated)and either permanently attached or attached (e.g., detachable) whenneeded.

Accordingly, there is shown a positioning system that allows images ofthe identified region of interest to be captured with differentgeometries, x-ray focus spot sizes, or other acquisition systemparametric variations that can produce images of the ROI havingdifferent characteristic properties.

The method is generally illustrated in the flow diagram shown in FIG.11. As illustrated, using an x-ray imaging system, a first x-ray imageof a chest I-1 is captured and a region of interest ROI-1 is identifiedwithin the first image I-1. The x-ray imaging system is then configuredto capture another x-ray image I-2 of the same region of interest usinga different acquisition system parameter. For example, bytranslating/rotating/moving the x-ray source (such as shown in FIG. 7)or using a different x-ray source (such as shown in FIG. 8) so as tocapture an image of the identified region of interest using differentgeometries, x-ray focus spot sizes, or other acquisition systemparametric variations to produce an image of the ROI having differentcharacteristic properties.

This is repeated wherein a plurality of images are acquired, each imageincluding the same/identified region of interest, but captured using adifferent acquisition system parameter.

Still referring to FIG. 11, a processing engine is employed to extractfeatures from each of the ROI of the images. The extracted features arethen analyzed using an analyzer such as a statistical predictive modelor trained neural network. Such processing engines, statisticalpredictive models, and trained neural networks are known to thoseskilled in the art. Training is performed using prior images fromdifferent patients acquired on portable imaging systems and othermodalities such as CT where the ground truth is known. Features such atexture, opacity, pixel value, and the like, are extracted to providebiomarkers (i.e., quantitative features) and correlated with differentdiseases. The information provided by the features is improved by theincreased amount/number of ROI images acquired under different imagingconditions. Features that provide the best/optimum predictive models forvarious diseases are identified and yield an index for each diseaseswhich correlates with the probability of each disease being present.

A disease probability output is generated which provides anindicator/representation/index of the probability of the disease. Forexample, that the opacity is indicative of a specified underlying cause.This output can be displayed on display 32 or other visual device. Thoseskilled in the art will recognize that the output can be numerical,index, iconic, graphical, color coded, in the form of a chart orillustration, or the like.

FIG. 12 provides an example wherein features are extracted to evaluatepleural effusion causes, such as blood, pus, and water. A pleuraleffusion cause comparison test is accomplished, scores are compared, andresults are displayed.

FIGS. 13A and 13B show examples of a display output which comparesscores and displays results. The features are extracted and theprobability for each cause is computed from which an index is generatedand provides a relative score that indicates to the user which possiblecause of the pleural effusion is most likely based on the extractedinformation.

It is noted that the method is not limited to conventional digitalportable X-ray imaging systems, but can also be employed by non-portablesystems.

In at least one arrangement, the method employ images of the ROI fromother/multiple modalities, including but not limited to, ultrasound,photon counting systems with energy discriminating capability,photo-acoustic imaging, and limited angle tomosynthesis.

In some arrangements, it may be desired to employ contrast media.

In some arrangements, it may also be desired to employ image processingtechniques such as rib suppression since it may be achieve greaterperformance.

Applicants recognize that other approaches for imaging the ROI includemulti-frame averaging to achieve a high signal-to-noise ratio (SNR).

The system may be used for real time x-ray imaging (e.g., fluoroscopyfor the ROI) and real time tomosynthesis imaging of the ROI, which mayhave benefits for imaging in the operating room, or for supportingbedside interventional procedures such as tube and line placements.

In the following description, a preferred embodiment of the presentinvention will be described as a software program. Those skilled in theart will recognize that the equivalent of such software may also beconstructed in hardware. Because image manipulation algorithms andsystems are well known, the present description will be directed inparticular to algorithms and systems forming part of, or cooperatingmore directly with, the method in accordance with the present invention.Other aspects of such algorithms and systems, and hardware and/orsoftware for producing and otherwise processing the image signalsinvolved therewith, not specifically shown or described herein may beselected from such systems, algorithms, components and elements known inthe art.

A computer program product may include one or more storage medium, forexample; magnetic storage media such as magnetic disk (such as a floppydisk) or magnetic tape; optical storage media such as optical disk,optical tape, or machine readable bar code; solid-state electronicstorage devices such as random access memory (RAM), or read-only memory(ROM); or any other physical device or media employed to store acomputer program having instructions for controlling one or morecomputers to practice the method according to the present invention.

The methods described above may be described with reference to aflowchart. Describing the methods by reference to a flowchart enablesone skilled in the art to develop such programs, firmware, or hardware,including such instructions to carry out the methods on suitablecomputers, executing the instructions from computer-readable media.Similarly, the methods performed by the service computer programs,firmware, or hardware are also composed of computer-executableinstructions.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In this document, the terms “including” and “inwhich” are used as the plain-English equivalents of the respective terms“comprising” and “wherein.” Also, in the following claims, the terms“including” and “comprising” are open-ended, that is, a system, device,article, or process that includes elements in addition to those listedafter such a term in a claim are still deemed to fall within the scopeof that claim.

In the following claims, the terms “first,” “second,” and “third,” andthe like, are used merely as labels, and are not intended to imposenumerical requirements on their objects.

The invention has been described in detail with particular reference toa presently preferred embodiment, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention. The presently disclosed embodiments are thereforeconsidered in all respects to be illustrative and not restrictive. Thescope of the invention is indicated by the appended claims, and allchanges that come within the meaning and range of equivalents thereofare intended to be embraced therein.

1. A digital x-ray imaging system, comprising: an x-ray source adaptedto emit an x-ray beam; a collimator to collimate the x-ray beam to anidentified region of interest; a positioning system to translate orrotate the x-ray source from a first position to a second position,wherein the second position is different than the first position; adigital x-ray detector adapted to capture a first image of the region ofinterest when the x-ray source is in the first position, and capture asecond image of the region of interest when the x-ray source is in thesecond position; a processing engine to extract features from each ofthe region of interest of the first and second captured images; and ananalyzer analyzing the extracted features and generating an indicator ofa disease responsive to the extracted features.
 2. The system of claim 1wherein the identified region of interest of each captured image arecaptured with different geometries, x-ray focus spot sizes, or otheracquisition system parametric variations that can produce images of theregion of interest having different characteristic properties.
 3. Thesystem of claim 1 wherein the extracted features include texture,opacity, and pixel value.
 4. The system of claim 1 wherein the extractedfeatures evaluate pleural effusion causes of blood, pus, and water.
 5. Adigital x-ray imaging system, comprising: an x-ray source adapted toemit an x-ray beam; a collimator to collimate the x-ray beam to anidentified region of interest; a first x-ray source disposed in a firstposition; a second x-ray source disposed in a second position, whereinthe second position is different than the first position; a digitalx-ray detector adapted to capture a first image of the region ofinterest using the first x-ray source disposed in the first position,and capture a second image of the region of interest using the secondx-ray source disposed in the second position; a processing engine toextract features from each of the region of interest of the first andsecond captured images; and an analyzer analyzing the extracted featuresand generating an indicator of a disease responsive to the extractedfeatures.
 6. The system of claim 5 wherein the identified region ofinterest of each captured image are captured with different geometries,x-ray focus spot sizes, or other acquisition system parametricvariations that can produce images of the region of interest havingdifferent characteristic properties.
 7. The system of claim 5 whereinthe extracted features include texture, opacity, and pixel value.
 8. Thesystem of claim 5 wherein the extracted features evaluate pleuraleffusion causes of blood, pus, and water.
 9. The system of claim 5further comprising a display for displaying the indicator.
 10. A methodfor digital x-ray imaging, comprising: emitting a first collimated x-raybeam from an x-ray source disposed in a first position; directing thefirst collimated x-ray beam onto an identified region of interest (ROI)and capturing a first ROI image; emitting a second collimated x-ray beamfrom the x-ray source disposed in a second position, wherein the secondposition is different than the first position; directing the secondcollimated x-ray beam onto the identified region of interest andcapturing a second ROI image; processing the first and second ROI imagesto extract features from each of the first and second ROI images;analyzing the extracted features; generating at least one indicator of adisease responsive to the analyzed extracted features; and storing,displaying, or transmitting the at least one indicator.
 11. The methodof claim 10 wherein the first and second x-ray sources are the samex-ray source.
 12. The method of claim 10 wherein the first and secondx-ray sources are different x-ray sources.
 13. The method of claim 10wherein the identified region of interest of each captured ROI image arecaptured with different geometries, x-ray focus spot sizes, or otheracquisition system parametric variations that can produce images of theregion of interest having different characteristic properties.
 14. Thesystem of claim 10 wherein the extracted features include texture,opacity, and pixel value.
 15. The system of claim 10 wherein theextracted features evaluate pleural effusion causes of blood, pus, andwater.